1. Field of the Invention
The present invention relates to certain pyrazole-containing compounds which act as juvenile hormone mimics for pest control.
2. Description of the Background
Analogs of juvenile hormones, JH mimics, are known as candidates for pest control agents, against insects in particular. The search for such compounds with high activity, high stability, safety and ease of production has been intense. Juvenile hormone analogs have been regarded as third generation insecticides because they differ in their mode of action from other insecticides and they have low toxicity to non-target organisms. Such compounds can have an influence on every stage of insect development. For example, they can induce ovicidal effects, inhibit metamorphosis to the adult stage (death in the last larval or pupal stages), and interfere with molting of early instar larvae in certain insect species.
The first natural juvenile hormones to be identified structurally are referred to as JH 0-III. These compounds have the following structures: ##STR2## R=R.sub.1 =R.sub.2 =ethyl, JH 0; R=R.sub.1 =ethyl, R.sub.2 =methyl, JH I; R=ethyl, R.sub.1 =R.sub.2 =methyl, JH II; R=R.sub.1 =R.sub.2 =methyl, JH III.
It was later found that the isoprene unit in JH I bearing the methoxy-carbonyl function can be replaced by an appropriately substituted phenoxy group with retention of juvenile hormone activity. See "Scientific Papers of the Institute of Organic and Physical Chemistry of Wroclaw Technical University," No. 22, Conference 7, pages 289-302 (1981). The replacement of the homoisoprene units by a further phenoxy group gives rise to compounds of type 1, shown below, which also show good juvenile hormone activity. Similarly, substitution of the two homoisoprene units by phenoxy groups provides compounds of type 2 having good juvenile hormone activity. It has also been found that replacement of all three isoprenoid units, the two homoisoprene units and the isoprene unit, by phenyl groups can also mimic juvenile hormone activity. Such compounds are compounds 3 shown below. ##STR3##
The first juvenile hormone mimic insecticide commercially produced is known as "methoprene" (1). Methoprene 1 has a terpene skeleton. Its structure is as follows: ##STR4##
Other structures related to those shown above have been found to have juvenile hormone activity also. The compound known as Sumilarv.RTM. having the following structure: ##STR5## has been shown to have high juvenile hormone activity against various species of insects. It is particularly useful as a fly control agent.
The following thiolcarbamate compound has been shown to have high insect growth regulation activity: ##STR6## [Recent Advances in Insect Control, 1984, pp. 103-113].
Another compound shown to have insect growth regulating properties, known as fenoxycarb.RTM., has the following structure: ##STR7## Fenoxycarb is a non-neurotoxic insecticide which exhibits strong juvenile hormone activity against a variety of insects.
Compounds of the following structures have also been developed as potent insect juvenile hormone mimics. ##STR8## [J. Agric. Food Chem. 1988, 36, 378-384].
To date there have been no reports on juvenile hormone mimic compounds which contain pyrazole moieties. However, pyrazole-containing compounds have been used in the past for a variety of purposes. The following publications are exemplary.
U.S. Pat. No. 3,190,888 is directed to aryloxyalkylpyrazoles having pharmacological properties. In particular, the compounds are disclosed to be useful as hypoglycemic agents.
U.S. Pat. No. 4,717,734 is directed to aryl, aryloxy or arylthio(azolo-methanes) and their use as pesticides.
U.S. Pat. No. 4,151,293 is directed to insecticidal pyrazole-4-methanol esters.
DE No. 3,122,174 is directed to azoloyl-methyl ethers that have plant growth regulating and herbicidal activity.
U.S. Pat. Nos. 4,663,341, 4,689,337, 4,742,060, and Chemical Abstracts 86,12644 each disclose pyrazole-containing compounds which might be used as insecticides.
In spite of the above background, there remains a need for juvenile hormone mimic compounds which can be used to regulate insect growth.